Author Topic: Sanding Sealer, Part II  (Read 65 times)

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SpaceMouse

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Sanding Sealer, Part II
« on: January 30, 2018, 04:39:11 PM »
Having just re-entered the hobby after a 40 year hiatus, I'm noticing that times have changed.  After an hour or two of fruitless internet searching, it appears that the old Aero Gloss sanding sealer is essentially extinct, having been killed off by the arguably necessary crackdown on VOCs.  From what I've been able to glean from internet reviews, the water-based replacements (clear acrylic with baby powder filler?) leave a good bit to be desired, particularly in terms of not penetrating and hardening soft balsa like the old acetone and toluene laced butyrate sealers. 

So... any ideas as far as a suitable replacement?  I've re-finished a few old wood cased tube radios with shellac.  The thought occurs that it's got some similarly desirable properties- it soaks into the wood, adds (insect shell based) hardeners to the wood, and leaves a smooth, sandable finish.  Has anyone tried shellac (with or without talc filler) as a sanding sealer substitute, or any other concoctions that work better than the water-based ersatz sealer?

Thanks
Sniffing dope since 1968

lastvautour

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Re: Sanding Sealer, Part II
« Reply #1 on: January 31, 2018, 05:39:39 AM »
I use acrylic wax with talc powder to mixed results on balsa. Lately it has been rial and error.

Lou
« Last Edit: February 01, 2018, 08:28:42 AM by lastvautour »

johnnytodd

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Re: Sanding Sealer, Part II
« Reply #2 on: February 01, 2018, 06:31:50 AM »
Not sure how it would mix with acrylic paint but Durham's water putty has a talc consistency and fills holes nicely - probably stronger than just talc.  Durham's is available at most hardware stores and Amazon $4.00   I work in basswood and seal all my models with automotive sandable spray primer exclusively, sanding between coats.


SpaceMouse

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Re: Sanding Sealer, Part II
« Reply #3 on: February 01, 2018, 07:05:43 AM »
Interesting idea.  Since both are water based, I wouldn't anticipate compatibility issues.  And Durham's does indeed set up rock hard.  I think this combination would leave a smooth, hard finish.  Still interested in finding something that would soak into the balsa and harden it.
Thanks!
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Model Maker

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Re: Sanding Sealer, Part II
« Reply #4 on: February 02, 2018, 02:15:08 PM »
Hi SpaceMouse

A couple of approaches come to mind. The first one is shellac. It dries hard, soaks into the wood well and should be able to handle adding talc. It is fast drying. I use it as a sealer on all my models to seal in pitch. Shellac is a great primer for oil and acrylics. It also dries quickly. I normally dilute the first and second coats with alcohol to promote absorption. But it can be used undiluted if required. It comes in clear, orange and Zinser makes a white.

You could also consider an oil based urethane varnish with talc. As with shellac, I dilute the first couple of coats with thinner. However, urethane takes longer to dry than shellac and is initially softer than shellac. You should also be able to add talc to thicken up to fill the pores of the balsa similar to shellac.

If I had to choose between the two options, I'd go for shellac since it's drying time and hardness are closer to the older sealers than urethane.

-ken
« Last Edit: February 02, 2018, 02:23:32 PM by Model Maker »

Oceaneer99

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Re: Sanding Sealer, Part II
« Reply #5 on: February 02, 2018, 03:38:07 PM »
I've been using a lacquer-based sanding sealing, to which I add more talc.  But it's possible that lacquer may not be available where you live (I live in the US).

I have a small bottle of clear nail polish (the lacquer type) that I added talc to and use with the built-in brush to seal very small parts. 

I have also used CA adhesive to harden sharp edges (like carved inlets where the edges are very thin). I mostly work in basswood.

Garet

SpaceMouse

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Re: Sanding Sealer, Part II
« Reply #6 on: February 09, 2018, 04:28:09 PM »
Great suggestions, thanks!
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lastvautour

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Re: Sanding Sealer, Part II
« Reply #7 on: February 10, 2018, 02:25:18 PM »
I have used lacquer based sealer to good effect when I was building balsa flying models but suddenly found that this is no longer stocked in the hardware stores I frequent. Water base products are widely available. Lacquer product can't be mailed but I imagine with lots of money it can probaly be sent by courrier. My budget precludes that option.

Lou